An increasingly important goal in the automotive industry is improved fuel efficiency. This goal is accomplished, in part, through the use of lightweight materials in the construction of vehicle component parts. Lightweight parts are increasingly used in the internal combustion engine itself. This includes the use of lightweight intake and exhaust valves. In addition to reducing fuel comsumption, lightweight engine valves can also enhance high speed engine performance.
Construction of lightweight engine valves has been approached in a number of different ways. U.S. Pat. Nos. 4,928,645 to Berneburg et al and 4,881,500 to Kojima et al disclose engine valves constructed from ceramic materials. U.S. Pat. No. 4,834,036 to Nishiyama et al discloses a composite engine valve having various parts constructed from titanium aluminum alloys and steel. U.S. Pat. No. 4,433,652 to Holtzberg et al discloses a composite engine valve having parts constructed from titanium, steel, or aluminum as well as thermoplastics
Each of the above noted inventions succeed in reducing the weight of the engine valve. However, each also suffer various problems For example, engine valves having ceramic valve heads are less able to withstand wear resulting from repetitive pounding against the valve seat. This problem can be solved through the use of composite engine valves having metal alloy valve heads combined with a valve stem of lightweight materials or construction. Known composite engine valves, however, suffer from inherent problems associated with tension and rotational forces acting upon the joint between the valve head and the valve stem.
These and other problems encountered by the prior art are addressed by the invention as described below.